Cumulative effect of multiple loci on genetic susceptibility to familial lung cancer.

BACKGROUND Genetic factors play important roles in lung cancer susceptibility. In this study, we replicated the association of 5p15.33 and 6p21.33 with familial lung cancer. Taking into account the previously identified genetic susceptibility variants on 6q23-25/RGS17 and 15q24-25.1, we further determined the cumulative association of these four genetic regions and the population attributable risk percent of familial lung cancer they account for. METHODS One hundred ninety-four case patients and 219 cancer-free control subjects from the Genetic Epidemiology of Lung Cancer Consortium were used for the association analysis. Each familial case was chosen from one high-risk lung cancer family that has three or more affected members. Single nucleotide polymorphisms (SNP) on chromosomal regions 5p15.33, 6p21.33, 6q23-25/RGS17, and 15q24-25.1 were assessed for their associations with familial lung cancer. The cumulative association of the four chromosomal regions with familial lung cancer was evaluated with the use of a linear logistic model. Population attributable risk percent was calculated for each SNP using risk ratio. RESULTS SNP rs31489 showed the strongest evidence of familial lung cancer association on 5p15.33 (P = 2 x 10(-4); odds ratio, 0.57; 95% confidence interval, 0.42-0.77), whereas rs3117582 showed a weak association on 6p21.33 (P = 0.09; odds ratio, 1.47; 95% confidence interval, 0.94-2.31). Analysis of a combination of SNPs from the four regions provided a stronger cumulative association with familial lung cancer (P = 6.70 x 10(-6)) than any individual SNPs. The risk of lung cancer was increased to 3- to 11-fold among those subjects who had at least one copy of risk allele at each region compared with subjects without any of the risk factors. These four genetic regions contribute to a total of 34.6% of familial lung cancer in smokers. CONCLUSIONS The SNPs in four chromosomal regions have a cumulative and significant association with familial lung cancer and account for about one-third of the population attributable risk for familial lung cancer.